Chemistry 2

Table of Contents

Intermolecular Forces

Changes in Matter

Solutions

Chemical Kinetics

Acids & Bases

Thermodynamics

Electrochemistry

Radioactivity

Intermolecular Forces

Types of Intermolecular Forces

Intermolecular forces: Forces between molecules, atoms, or particles

Can be attractive or repulsive

Are generally weaker than bonding forces

Relates to Coulomb’s law:

E =

=

Dispersion forces (London forces)

Occurs in all molecules and atoms

Created by the variability in the distribution of electrons outside the nucleus

Electrons are randomly arranged at any one point in time

The arrangement creates a temporary/instantaneous dipole

The magnitude is dependent on the ease of polarization of electrons

Polarize: Form a dipole moment

Depends on the molar mass and the molecular Shape

Polarity

Polarity depends on differences in electronegativity (ΔEN)

Electronegativity: Ability of an atom to attract electrons

Nonmetals have higher electronegativity than metals

ΔEN > 2.0: Ionic bond (nonpolar); electrons are transferred

ΔEN 0–0.4: Covalent bond (nonpolar); electrons are shared equally or nearly equally

ΔEN 0.4–2.0: Covalent bond (polar); electrons are shared unequally

Polar molecules have electron-rich and electron-poor areas

Polarity helps determine liquids’ miscibility, the ability to mix

Practical applications

Water is a polar molecule and grease and oil are nonpolar, so they don’t mix

One end of a soap molecule is polar and the other nonpolar, so soap can attract both water and grease

Dipole-dipole force

Occurs in all polar molecules, which have:

A permanent dipole

Dispersion forces

Higher melting and boiling points

Hydrogen bonding

Occurs in polar molecules with hydrogen atoms

Is the strongest of all intermolecular forces

Has a strong dipole-dipole attractive force

Hydrogen atoms bond with fluorine, nitrogen, and oxygen

Water has hydrogen bonds—without it, all Earth’s water